When a Fowler-type motion associated with flap extension is desired (i.e., rearward and rotational downward flap movement), most of the low-weight flap deployment mechanisms need to cross the aerodynamic shape of the clean wing configuration. These flap mechanisms do not have an aerodynamically friendly shape and thus the mechanisms induce drag forces when exposed to the airflow (especially during cruise flight phase). It is therefore typical for fairings to be provided so as to house the flap operating mechanisms (conventionally termed “flap track fairings”). Flap track fairings have two main functions, that is (1) to reduce the drag that would be caused by the flap deployment mechanism exposed to the airflow during the cruise flight phase (e.g., by smoothing the change in cross-sectional area of the mechanism), and (2) to protect the mechanism thus reducing the probability of hazardous events that may preclude deployment when needed. The flap track fairing must be provided with minimal profile so as to be more aerodynamically clean thereby promoting more economical (lower) fuel burn for the aircraft and improving the lift force during take-off and landing.
A flap track fairing needs to be designed such that it absorbs the movement of the flap deployment mechanism by avoiding structural interference during the flap extension/retraction cycle. Aircraft with swept wings commonly have a flap mechanism that is not aligned with the airstream such that there is some lateral travel of the deployment mechanism's movable components relative to the oncoming airstream that occurs with the flap extension. The outcome of such a scenario is usually addressed by designing a pivoted flap track fairing such that the lateral travel of the deployment mechanism's movable components is confined within the width of the flap track fairing. When appropriately designed and sealed, such a flap track fairing solution has the benefit of providing more efficient fuel burn as well as generating low ambient noise during the approach and landing flight phase when flaps are deployed.
Although, both the fuel burn benefit and the wing flap lift force efficiency of the conventional pivoted flap track fairing is limited by the width of the flap track fairing, it follows that, because of the restriction of a minimum width that will accommodate the lateral travel of the deployment mechanism's movable components, an increase in the flap track fairing frontal profile thickness is necessary thereby producing more drag force and more detached flow area on the suction side of the wing flap. The embodiments disclosed herein overcome the fuel burn benefit limitation and recovery of effective wing flap area that are found in conventional systems thereby making it possible for flap track fairings to have a relatively thinner frontal profile as compared to conventional proposals.